1. Field of the Invention
The present invention relates to an optical fiber and an optical communication system including the same.
2. Related Background Art
A non-zero dispersion-shifted fiber (NZDSF) is known as an optical fiber used as a signal light transmission path in an optical communication system. NZDSF has positive chromatic dispersion and small but non-zero absolute values of chromatic dispersion in the entire range of the C-band (wavelengths of 1530 to 1565 nm) and the L-band (wavelengths of 1565 to 1625 nm).
It is expected that such NZDSF has the preferred characteristics as described in LEAF Optical Fiber Catalog, Corning Incorporated (Non-Patent Document 1), as to the chromatic dispersion, dispersion slope, mode field diameter, effective area, cable cutoff wavelength, bending loss, and so on. Japanese Patent No. 4393708 (Patent Document 1) and Japanese Patent Application Laid-Open No. 10-293225 (Patent Document 2) disclose the optical fibers having such preferred characteristics.
The optical fiber disclosed in Patent Document 1 has a core consisting of three segments. The three segments consist of a first segment with an α-power index profile, and a second segment and a third segment provided around the first segment and each having a step index profile. The optical fiber disclosed in Patent Document 2 consists of a center core, a first ring provided on the outer periphery of the center core, a second ring provided on the outer periphery of the first ring and having the refractive index lower than the center core and higher than the first ring, a third ring part provided on the outer periphery of the second ring and having the refractive index higher than a cladding, and the cladding provided on the outer periphery of the third ring part.